1. Field of the Invention
The present invention relates to a liquid ejection recording unit and a liquid ejection recording apparatus.
2. Description of the Prior Art
FIG. 1 shows an example of the configuration of a liquid ejection apparatus.
Referring to FIG. 1, a liquid ejection recording unit 1 is mounted on a carriage 2 and has a container for containing ink therein and a recording head having a nozzle section for ejecting the ink. The units are arranged in a number corresponding to the number of inks of different colors to be used for recording or printing.
A flexible cable 6 connects between a control section (not shown) for controlling ink ejection and the liquid ejection recording unit 1.
A paper feeding motor 8 drives rollers 10 to convey a recording sheet P in a direction indicated by arrow f. Rollers 12 together with the rollers 10 keep the recording sheet P flat and thus define a recording surface with respect to the unit 1.
A belt 14 has the carriage 2 fixed thereon for driving it. A motor 16 drives the belt 14 in directions indicated by arrow S. When the carriage 2 is driven by the motor 16, it is moved along guide rails 18 in the directions of the arrow S so as to record on the recording surface.
In the liquid ejection recording unit mounted on the carriage of such a liquid ejection recording apparatus, when the unit is mounted on the carriage, the interior of the ink container communicates with the atmosphere so as to allow ink ejection from the nozzle section.
In a conventional liquid ejection recording unit, when the unit must be stored for a long period of time or transferred from one location to another, an opening for replenishing the container with ink is closed with a closing member. When the unit is mounted on the carriage, the closing member is removed to allow communication of the opening with the outer atmosphere and to allow ink ejection from the nozzle section.
The closing member conventionally comprises, for example, a rubber stopper or a water-repellent filter. However, when a rubber stopper is used as the closing member, the operator must remove it by hand. However, since a liquid ejection recording unit is generally small in size, removal of the stopper is not easy and the portion surrounding the opening may be contaminated with ink. Conversely, even if a water-repellent filter is used as the closing member, the filter tends to clog when the carriage is being driven. This results in insufficient supply of air to the ink container.
FIG. 2 shows another example of the configuration of a conventional liquid ejection recording unit 1 different from the above-mentioned unit which is normally communicated with outer atmosphere. An ink container 23 contains ink 24 and supplies it to a nozzle section 22. An air layer 28 is formed at the upper surface portion of the ink 24 in the container 23. A diaphragm 26 is a pressurizing means for the ink container 23 so as to prevent clogging of the nozzle section and to prevent introduction of air bubbles. A communication hole 25 communicates between the ink container 23 and an air chamber 29 defined by the diaphragm 26. A communication hole 27 is formed in the diaphragm 26 so as to communicate the air chamber 29 with the outer atmosphere.
The conventional liquid ejection unit 1 shown in FIG. 2 has a pressurizing mechanism so as to recover the ejection capacity of the nozzle section when the nozzle section clogs or air bubbles are introduced. As such a pressurizing mechanism, a diaphragm is arranged outside the ink container. When the diaphragm is depressed, ink contained in the ink container is pressurized and the ejection capacity of the nozzle section is recovered.
In the conventional pressurizing mechanism as described above, the operator closes the communication hole 27 while he depresses the diaphragm 26. Then, the air layer 28 is compressed through the communication hole 25, and the ink 24 is pressurized so as to recover the ejection capacity of the nozzle section 22.
However, in the conventional liquid ejection recording apparatus having such a pressurizing mechanism, as the ink 24 inside the container is depleted, the pressurizing capacity obtained with the diaphragm 26 is unavoidably changed. More specifically, in the conventional liquid ejection recording unit, the pressurizing pressure fluctuates widely in accordance with a change in the volume of the air layer 28 and the ejection capacity is thus rendered unstable (first problem).
In order to maintain a sufficient pressurizing capacity when the ink 24 is depleted and the volume of the air layer 28 is increased, the pressurizing efficiency of the diaphragm 26 must be increased. Therefore, a second problem arises in that the liquid ejection recording unit is rendered bulky, while the first problem of unstable ejection capacity remains.
When a detachable liquid ejection recording unit of a conventional liquid ejection recording apparatus is stored during a non-usage period, for example, when the unit is replaced with another unit for printing in a different color ink or when the unit must be transferred from one location to another, the opening of the nozzle section and the communication hole must be closed to prevent leakage of ink therefrom. In the nozzle section, the orifice opening generally has a diameter of 100 .mu.m or less so that leakage can be prevented by the surface tension of the ink. However, compared with the nozzle section, the air communication hole has a large sectional area. When the unit is tipped over during storage or the like, ink leakage occurs and the storage location is contaminated. The air communication hole can be closed with a rubber stopper but this entails an extra step on the part of the operator.